Many well characterized metalloenzymes are found to contain metal clusters in or near the active sites, and these clusters often exist as bridged biological assemblies where a metal containing cluster is linked to alternate clusters via covalent bridging ligands. The Synthetic Analogue Approach will be used in the design, synthesis, characterization and reactivity studies of biologically relevant Fe/S and Fe/M/S (M = Mo, V, Ni) clusters in the hopes of preparing functional model complexes. These model complexes may provide insight into the important steric constraints provided by the polypeptide and electronic properties of the clusters (such as redox potential and electron transfer characteristics). A primary focus of this research will be the design of sulfur containing chelating ligands that may provide metal coordination environments similar to those found in the recently characterized iron-molybdenum cofactor of nitrogenase.